This relates generally to image sensors, and more specifically, to image sensors configured to produce high dynamic range (HDR) images.
Modern electronic devices such a cellular telephones, cameras, and computers often use digital image sensors. Imagers (i.e., image sensors) are formed from a two-dimensional array of image sensing pixels. Each pixel may include a photosensor such as a photodiode that receives incident photons (light) and converts the photons into electrical charges. Conventional image pixel arrays include frontside illuminated image pixels or backside illuminated image pixels. The image sensors may include photodiodes and other operational circuitry such as transistors formed in a front surface of the substrate. A single image sensing pixel in the two-dimensional array of image sensing pixels includes a single photosensitive region, a color filter formed over the photosensitive region, and a single dome-shaped micro-lens formed over the color filter.
Conventional imaging systems may have images with artifacts associated with low dynamic range. Scenes with bright and dark portions may produce artifacts in conventional image sensors, as portions of the image may be over exposed or under exposed. Conventional imaging systems may also have a lower signal-to-noise ratio than desired.
It would therefore be desirable to provide image sensors having improved dynamic range with reduced noise.